Ernestos are spherical purple robots with black and purple limbs, a black spherical head with a cycloptic eye, and a black tie paired with a matching top hat. Under the hat is a single spike. He also has very sharp, white fingers.
They are so bureaucratic that they're unable to do anything without filling out the proper paperwork first. They have also never taken vacation days. Ernestos are usually seen chatting around the office cooler. Though not used to fighting, Ernestos are surprisingly powerful in battle when given the proper motivation.
- Office/Business-themed attacks: Ernestos are able to use attacks based on office work. However, they have yet to be seen using these attacks in the series so far.
- Ball form: Ernestos have the ability to roll around in a ball form. They enter this form by retracting their head and limbs.
- Divide: Ernestos can split their bodies at the waist and attack in two locations at once.
- "Lakewood Plaza Turbo"
- "Let's Be Friends"
- "Stop Attacking the Plaza"
- "The Power Is Yours!"
- "Let's Watch the Pilot" (pilot design)
- "Lad & Logic" (flashback)
- "OK Dendy! Let's Be K.O.!"
- "Plaza Shorts 1"
- Ernesto's voice actor Christopher Niosi also voices Neil, Pird, and Nick Army.
- Out of the four characters he voices, Chris has stated that Ernesto is his favorite.
- In "Let's Be Friends", when K.O. was sneaking round Boxmore dressed as a robot and making beeping sounds, a pair of Ernestos asked each other "Should we be offended by that?" in reference to racial stereotypes and old depictions of sci-fi robots.
- Ernesto was the second robot of Boxman's design to be introduced to the cast, after Darrell.
- Ernesto is the only one out of all the Boxbots that calls Lord Boxman by his preferred name.
- So far, the only times Ernesto has been in fighting action is at the end of "Stop Attacking the Plaza" when Boxman sent him out with the rest of his siblings and in "OK Dendy! Let's Be K.O.!" when he himself is sent to destroy the plaza.
- In OK K.O.! Let's Play Heroes, Ernesto is shown to have two eyes in a cutscene, though he still has only one eye throughout the rest of the game.